All of this kerfuffle about the previous fire being somehow related to this failure may be completely unrelated to the bridge failure. A simple derailed loaded car (like the one in the river?) could have been off of the rails before the bridge but finally began to twist and turn and knocked the girder section off of its supports. I've seen that one. Had nothing to do with the bridge condition, except for the bridge being part of the damages caused by the derailment.

I also should note that fires on creosote pilings tend to burn the outside, like the "wick" of a candle. That is, the temperature of the burn, causes the creosote to turn into flammable gases, and burn, while not burning the "wood" underneath, which is acting as a "wick". When you blow the burning gases out, the wick is still there.

There was a fire many years ago at the bridge on the SP Alhambra main (and El Monte siding) over the Rio Hondo, just south of the El Monte Airport, that caught fire, and that looked like the whole wooden trestle portion of the bridge was on fire. But it was only the surface creosote of the that wood was actually the fuel source of the fire.

I seem to even recall that I was told by one of the MOW managers, when working the San Gabriel switcher, that it caused the creosote to liquify and bubble out. And that when the fire stopped, that the burnt creosote hardened and turned into a "plastic" like consistency. And that this actually made the bridge even more impervious to rot and decay, leaving the structural integrity completely unaffected.

When we know the sequence of events leading up to this, and what exactly failed to precipitate the collapse, I suspect that it will improve the quality of the speculation considerably.

My question, to improve the quality of speculation, for locals who may know something about this particular bridge, would be: Was the center steel section of the bridge now in the river held up by wooden bents or concrete piers?